Replies

1. 
   Ragnar17 | Jun 21, 2007 08:24am | #1

   Can't you just miter them without resorting to a compound setup?  Maybe if you had a picture of the trim element I could help more.

1. 
   alrightythen | Jun 21, 2007 08:53am | #3

   I'll try and get a picture tomorrow. but essenstionaly it's the same idea as if you were to bevel cut sheets of plywood when sheeting a hip roof along the hip.

   it is not a 45 degree, the steeper the roof pitch gets ( or angle) the sharper miter gets. and the bevel also changes from 0 degree when laying flat to sharper as the angle gets gets higher. 

   I don't know what the formula is, I've always just figured it out by trial and error    View Image                                          View Image    

2. 
   alrightythen | Jun 21, 2007 06:51pm | #5

   Photos as requested

       View Image                                          View Image    

1. 
   JoeBartok | Jun 21, 2007 07:13pm | #6

   Alrightythen, are you are making the cut along the slope? If so, the procedure is the same as cutting SIPs or insulation for a Hip roof.

   You know the slopes as viewed in section; these are the equivalent of the pitches of the common rafters for a Hip roof. The angle at the corner is 90°.

   The angle on the surface of the slope is the "Sheathing Angle", the saw blade bevel is the "Backing Angle".

   There were a couple of related threads recently. I'll see if I can find the link and post it.

   Joe Bartok

   Edited 6/21/2007 12:14 pm ET by JoeBartok

1. 
   JoeBartok | Jun 21, 2007 07:23pm | #7

   It's going to take too long to find the threads so here's a picture of the "hopper angles" I posted.

   This will help you solve the angles: Roof Framing and Joinery Angle Calculator

   Enter the pitches (slopes as viewed in section) and the angle in the corner in plan view.

   The angle on the face is 90° – P2 (Sheathing Angle), the saw blade angle is C5 (Backing Angle).

   Something just occured to me: is it the angle on the face and the corner which are givens and you need to calculate from these values?

   Looking at the photos it looks like the angle in the corner is 90° and the slopes are equal so the "Plan Angle" to each side of the ridge is 45°. If we call the angle measured on each face the "Sheathing Angle", the equation for the saw blade bevel (the "Backing Angle") is:

   Backing Angle = arccos (sin Plan Angle ÷ sin Sheathing Angle)

   Again, all of this is based on the assumption that you are making the cut with the saw travelling along the angle on the sloped face.

   Joe Bartok

   Edited 6/21/2007 12:24 pm ET by JoeBartok

   Edited 6/21/2007 12:30 pm ET by JoeBartok

   Edited 6/21/2007 12:31 pm ET by JoeBartok

   Edited 6/21/2007 12:34 pm ET by JoeBartok

2. 
   alrightythen | Jun 21, 2007 07:45pm | #8

   Thanks Joe,

   I did a search and didn't find much...without spending hours anyway. You are onto what I am looking for. have never worked with SIP or cut insulation for hips. but I have worked with these kinds of angles before using trial and error.   View Image                                          View Image    

1. 
   JoeBartok | Jun 21, 2007 08:02pm | #9

   Here's one of the links:

   http://forums.taunton.com/tp-breaktime/messages?msg=88812.1Joe Bartok

2. 
   Ragnar17 | Jun 22, 2007 04:46am | #10

   Thanks for posting the pics.

   It looks like you've already got your solution using trigonometry.  There are some sharp framers at this board.

   An alternative method would be to use crown stops on your chop saw.  (See picture in case you don't know what I'm talking about.)  I'm not sure what method will work best for you, but the thing I like about the crown stop approach is that it's much easier to tweak your angle if needed.  That is, you just make a single quick adjustment to the primary angle of your chop saw.  I use this approach a lot because the chop saw I most often use only tilts one way, and flipping long pieces of crown gets annoying pretty quickly.

    

   View Image

    

1. 
   alrightythen | Jun 22, 2007 06:42am | #11

   yeah...Joe...is sharp guy I've gotten very useful info from him in the past.

   I like the crown stop idea.. as long as you have it set up how you want the slope...make your cut at 45 and you are set.

   I still like to know the math though   View Image                                          View Image    

1. 
   Ragnar17 | Jun 22, 2007 10:26am | #12

   What slope angle are you setting your pier caps at? 

   Edited 6/22/2007 3:26 am ET by Ragnar17

2. 
   alrightythen | Jun 22, 2007 03:00pm | #13

   don't know yet.. I have to do some coming up soon. but really I asked because my neighbour asked me what the formula was. I told him I always winged it.

   but it is a shallow slope similar to photos. only a few degrees.

    

      View Image                                          View Image    

   Edited 6/22/2007 8:01 am by alrightythen

3. 
   HootOwl | Jun 22, 2007 04:17pm | #14

   You might find these handy.

4. 
   JoeBartok | Jun 22, 2007 05:52pm | #15

   Those diagrams reminded me of something:

   Frank Martindale's Hip and Valley Book

   Joe Bartok

   Edited 6/22/2007 10:53 am ET by JoeBartok

2. 
   AaronRosenthal | Jun 21, 2007 08:35am | #2

   I don't know if this will help, you may already have it.
   http://www.josephfusco.org/

   Quality repairs for your home.

   AaronR Construction
   Vancouver, Canada

    

1. 
   alrightythen | Jun 21, 2007 09:08am | #4

   Thanks Aaron, I didn't have that site. I'm trying to equate the crown formula to the reverse ( upside down) I know it should work But I'm too tired to figure it out. and I didn't think I needed a scientific calc to get the spring angle. I think I can get that more easily with a protractor.   View Image                                          View Image